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Genetics. The Language of Life. Image from: http://commons.wikimedia.org/wiki/File:Hazel_eye.jpg. Define Genetics!. Genetics, The Unit. How these genes are passed from generation to generation. ( inherited ) How genes affect the way we look and Function. - PowerPoint PPT Presentation
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GeneticsThe Language of Life
Image from: http://commons.wikimedia.org/wiki/File:Hazel_eye.jpg
Define Genetics!
Genetics, The Unit• How these genes are passed from
generation to generation. (inherited)• How genes affect the way we look and
Function.• What’s the probability of a gene being
inherited?• How we can manipulate genes to get
desired outcomes
Genetics, ClarifiedHow we get the Genes we get (Genes?)
Gene: A section of DNA that encodes for a trait. (Trait?)
Trait: Information communicated by the DNA. Sometimes obvious (eye color), sometimes hidden (enzymes).The gene is a sequence of the DNA, the trait is what the DNA encodes for, or “makes”.
For example: Eye colorAlleles: The different “forms” a gene may have
Important point: a gene actually encodes for a protein.“One gene: one protein”
http://commons.wikimedia.org/wiki/File:Chromosomes.JPG
Organization in the Nucleus
• Long strands of chromatin condense into chromosomes.
• The sister chromatids are the result of replication.
• Each chromatid has the same base sequence
• Histone proteins act as spools
http://upload.wikimedia.org/wikipedia/commons/9/91/Chromosome.gif
ChromosomesChromosomes are generally represented as being shaped like an “X”.
The spot where the 2 chromatids join is called the centromere
The shorter part of the “X” is the “p” arm
The longer part of the “X” is the “q” arm
They are actually 2 chromatids joined together like conjoined twins. The result of replication of one chromatid
Chromatid
How many?
Most of the cells in our body have 46 (23 pair) chromosomes.
Exception:
Our Gametes (egg and sperm) have 23 single chromosomes
How many?
Gametes
Diploid Zygote (fertilized egg)
(haploid)
Some Vocabulary• Gene
• Allele
• Zygote
• Gamete
Section of DNA that codes for a trait (actually, they code for protein strands but more on that later)
Different “forms” of a gene (brown eyes vs. blue eyes)
fertilized egg (alleles in pairs)
sex cells i.e. sperm and eggs (single alleles)
http://upload.wikimedia.org/wikipedia/commons/b/b7/Snow_Pea_on_Plant.JPG
http://www.nlm.nih.gov/visibleproofs/media/detailed/vi_a_201.jpg
Mendel A monk and his peas
• Mid 19th century Austrian• Developed a basic
understanding of inheritance of traits.
• Followed traits in generations of pea plants
Following the Traits
http://commons.wikimedia.org/wiki/File:Mendel_seven_characters.svg
Mendel’s “Laws”• Genes for traits come in pairs (one from each
parent).• Law of dominance – one gene (allele) can
prevent the appearance of another gene (allele).• Law of segregation – when gametes form,
pairs of genes separate so each gamete gets one of each gene pair.
• Law of independent assortment – During gamete formation, genes for different traits separate independently of one another.
More Vocabulary• Heterozygous • Homozygous
• Dominant
• Recessive
Having different alleles in an allelic pair (Bb) AKA hybrid
Both alleles in the pair are the same (BB, bb) AKA pure
The allele that is expressed (shown) in a heterozygous pair of alleles
The allele that is NOT expressed in the heterozygous pair of alleles
Even More Vocabulary• Phenotype
• Genotype
The physical traits that are expressed in an individual e.g. brown eyes
The alleles present in an individual e.g. BB or Bb
*Phenotype does not always show genotype
Brown eyes = BB or Bb
So how do we figure out our genotype? More on that…next class
For instance:
Homozygous red
Heterozygous red
Homozygous white
What’s the genotype?
The phenotype?
RR
Red
What’s the genotype?
What’s the genotype?
The phenotype?
The phenotype?
RrRed
rr
White
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